#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
    int n = 0;
    int arr[100] = { 0 };
    int i = 0;
    int j = 0;
    while (i <= n)
    {
        scanf("%d", &arr[i]);
        i++;
        n = arr[0];
    }
    for (i = 0; i <= n; i++)
    {
        int count = 0;
        for (j = 1; j <= n; j++)
        {
            if (arr[j] != i)
            {
                count++;
                if (count == n)
                {
                    printf("%d\n", i);
                }
            }
        }
    }
    return 0;
}